Transformer



May 11, 1937- s. M. LucAs ET AL TRANSFORMER Filed April 26, 1935 3 Sheets-Sheet l m 5 t 1 S W 2 H mm N E m 9 m M e a ua R m W SC T B C m w W a E 0 mi b h 5 0 ll Z Q r ll 1 W O Ma 11, 1937. a M LUCAS ET AL' 2,080,177

TRANSFORMER Filed April 26, 1955 5 Sheets-Sheet 2 I 7. 2 12 I I 32 I 16f T III II ill III III III. 18 I {I III "III 16 I C) n I I O? 21 I I I I I I l I I I I l I I I I I l I I l I I I I I g I l I I A l /I I I I I I 17? I 17 I --P 1 I I I I I I I I I I 5 I II I I I I I .l I I I O 7d INVENTORS Samuel M Lucas and Conrad H. Zierqiz. BY W W THEIR ATTO RN EY y 1937- s. M. LUCAS ET AL 2,080 177 TRANSFORMER Filed Apfil26, 1955 s Sheets-Sheet 3 mp1 III III Ii INVENTORS Samuel M Lucas and Uozzrad H Zierdt. MW

MIR ATTORNEY Patented May 11, 1937 UNITED STATES PATENT OFFICE TRANSFORMER Application April 26,

11 Claims.

Our invention relates to transformers, and particularly to reactive transformers having an adjustable equivalent reactance.

One object of ourinvention is the provision, in a transformer of the type described, of novel means for adjusting the equivalent reactance of the transformer, whereby the range of adjustment of the transformer is increased and a continuous adjustment is provided between the maximum and minimum reactance.

We will describe several forms of transformers embodying our invention, and will then point out the novel features thereof in claims.

In the accompanying drawings, Fig. 1 is a front elevational view showing one form of transformer embodying our invention. Fig. 2 is a left-hand end view of the transformer shown in Fig. 1. Fig. 3 is a top view of the transformer shown in Figs. 1 and 2. Fig. 4 is a detail view of the bracket l forming part of the transformer illustrated in the preceding views. Figs. 5 and 6 are front elevational and left-hand side views, respectively,

showing another form of transformer embodying our invention. Figs. '7, 8 and 9 are detail views showing certain of the laminations which are employed in constructing the core of the transformer shown in Figs. 5 and 6. Figs. 10 and 11 are front elevational and left-hand end views, respectively, showing a'third form of transformer embodying our invention. Figs. 12, 13 and 14 are front elevational, right-hand end, and top views, respectively, showing a fourth form of transformer embodying our invention.

Similar reference characters refer to similar parts in each of the several views.

Referring first to Figs. 1 to 4, inclusive, the transformer here illustrated, which transformer is designated as a whole by the reference character T comprises a stationary core member I of magnetizable material and a movable core member 2 which is also of magnetizable material. The stationary core member I is preferably laminated for obvious reasons, and comprises three vertically disposed spaced parallel legs I, I and l connected together at their lower ends by a backstrap l The middle leg I of the stationary core member I is surrounded by a primary winding P, while one of the outer legs, here shown as the leg I, is surrounded by a secondary winding S.

The movable core member 2 is also preferably laminated, and in the form here shown is substantially rectangular in shape. It is mounted for longitudinal sliding movement between two guide plates 3 and 4 which are secured to the op- 1935, Serial No. 18,306

posite sides of the stationary core member i, at the upper ends of the legs of this core member. by means of certain ones of the bolts 5 which fasten the laminations of the stationary core member together. Provided adjacent the oppo- 5 site ends of the movable core member 2 are through bolts 8 and l, which bolts secure the laminations of the movable core member together, and also cooperate with the inner ends of two pairs of aligned slots 3', 4 and 3, 4, provided in 10 the guide plates 3 and 4, to limit the extreme positions to which the core member 2 may be moved. To facilitate moving the core member 2, a screw-threaded rod 8 is provided. This rod is fastened at one end to the movable core member by means of the bolt 5, and is provided at the other end with a thumb nut 9 which is rotatably mounted in a lateral extension 3 formed on the guide plate 3. The portion of the thumb nut which rotates in the extension 3 has a smaller exterior diameter than the remainder of the thumb nut, whereby longitudinal movement of the thumb nut relative to the extension is prevented. It will be apparent that by turning the thumb nut in opposite directions the movable core member may be moved to any desired position between its two extreme positions. A bolt l0 passes through the plates 3 and 4 above the core member in such manner that by tightening this bolt the movable core member may be clamped in any desired position to which it is moved by the thumb nut.

With the transformer constructed in the manner just described, it will be apparent that two parallel flux paths are provided for the flux which is set up bythe primary windingP when this winding is energized, one of which paths passes through the secondary winding S and includes the left-hand half of the backstrap I as viewed in Fig. 1, the leg I", and the left-hand end of 40 the movable core member 2, and the other of which paths is a leakage path and includes the right-hand half of the backstrap I as viewed in Fig. 1, the leg I and the right-hand end of the movable core member 2. It will also be apparent that the flux which is set up in the core by the energization of the primary winding P will divide between the two paths just traced in proportion to the relative reluctances of these paths. The parts are so proportioned that when the movable core member occupies its extreme position in which it is shown in the drawings, the leakage path will have a relatively low reluctance and the path through the secondary winding will have a relatively highreluctance, whereas,

when the movable core member occupies its other extreme position, the leakage path will then have a relatively high reluctance and the path through the secondary winding will have a relatively low reluctance. It follows, therefore, that when the movable core member occupies the extreme position in which it is shown in the drawings, substantially all of the magnetic flux from the primary winding will traverse the leakage path, and under these conditions, the secondary winding will have its maximum reactance, and the voltage regulation of the transformer will be substantially the same as that of a constant potential transformer with maximum reactance in series with the secondary winding. When, however, the movable core member occupies its other extreme position, substantially all of the magnetic flux from the primary winding will then traverse the path through the secondary winding, and under these conditions, the secondary winding will have its minimum reactance, and the voltage regulation of the transformer will approach that of a constant potential transformer. It will readily be understood that by moving the movable core member between its two extreme positions, the reluctance of the two flux paths may be gradually varied between their maximum and minimum values, and that as the reluctance of one path increases, the reluctance of the other path will simultaneously decrease, and it is evident, therefore, that by changing the position of the movable core member 2, the equivalent reactance of the secondary winding S may be varied by infinitely small amounts to give any desired value between its maximum and minimum equivalent reactance, which value may be maintained by clamping the movable core member 2 in its adjusted position by means of the bolt l0.

As shown in Fig. 1, a portion of the movable core member 2 adjacent each end is cut away to provide an inclinedv surface 2. The function of these inclined surfaces is to cause the reluctances of the two magnetic paths to vary uniformly as the movable member is moved from either extreme position to the other extreme position.

Referring now to Figs. 5 and 6, we have shown a slightly different form of transformer which will produce the same results as the transformer T shown in Fig. 1. This transformer, which is designated as a whole by the reference character ,T comprises a magnetizable stationary core member II and a magnetizable movable core member l2. The stationary core member ll consists of a plurality of E-shaped laminations, each similar to the lamination l3 shown in Fig. 7, stacked on each side of, and secured to, a plurality of E-shaped laminations, each similar to the lamination l4 shown in Fig. 8. The laminations l3 are all stacked with their open ends extending downwardly, and are provided at their upper ends with slots l3 and I 3 which reduce the magnetic section between the middle and two outer legs. The laminations M are shorter than the laminations l3, and are each disposed with their open ends extending upwardly. With the stationary core member constructed in this manner, it will be apparent that it is provided with three vertically extending legs I I, II and ,ll the lower ends of which are connected together by a relatively low reluctance connection, and the upper ends of which are connected together by a relatively high reluctance connection. It will also be apparent that a channel H is formed at the upper end of the stationary member by virtue of the fact that the outer laminations of this core member arelonger than the inner laminations. The middle leg ll of the stationary core member II is surrounded by a primary winding P, and the outer leg II is surrounded by a secondary winding S.

The movable core member 12 comprises a stack of laminations each similar to the lamination l5 shown in Fig. 9. This core member is slidably mounted in the channel H and is provided with a longitudinally extending slot l5 through which a clamping bolt l6 that is mounted in the upper end of the stationary core member extends, whereby the movable core member may be locked in an adjusted position. The parts are so proportioned that when the movable core member occupies its right-hand extreme position in which it is shown in the drawings, the reluctance of the flux path which includes the leg II and which passes through the secondary winding 8 will be relatively high, and the reluctance of the leakage path, which path includes the leg II, will be relatively low, but that, when the movable core member occupies its opposite extreme position, the reluctance of the flux'path through the secondary winding will be relatively low and the reluctance of the leakage path will be relatively high. It follows, therefore, that by moving the movable core member I2 between its two extreme positions, the equivalent reactance of the secondary winding S of the transformer F may be varied in the same manner that the reluctance of the secondary winding 8 of the transformer T shown in Fig. 1 may be varied by moving the movable core member 2.

One feature of the transformer T is that the laminations at the top of the stationary core have a relatively large area in contact with the movable core member in all positions of the movable core member, thus causing the transformer to have a low magnetizing current.

Referring now to Figs. 10 and 11, the trans-- I and provided at their upper ends with aligned vertical tongues l8, l8 and. l8. The middle leg l'l of the stationary core member I! is surrounded by a primary winding P, and the outer leg I! is surrounded by a secondary winding S. The transformer T also comprises two movable laminated core members l9 and of magnetizable material which cooperate with the stationary core member on opposite sides of the tongues I8 I8 and I8. These movable core members are similar, and each is provided with a longitudinal slot 2! which slidably receives a clamping bolt 22 which is mounted in the middle tongue IS The movable core members are slidably supported on shoulders 23 which are formed on the legs Il ll and I1 on opposite sides of the tongues l8, l8 and l8, whereby the movable core members are held in horizontal positions.

With the transformer 'I constructed in the manner just described, it will be apparent that movement of either movable core member toward the right will increase the reluctance of the flux path through the secondary winding and will decrease the reluctance'of the leakage path, whereas movement of either movable core member in the opposite direction will produce the opposite effect. It will also be apparent that since each movable core member has a relatively small crosssectional area, a relatively large movement of either movable core member will produce a relatively small change in the relative reluctances of the two flux paths, thus providing a non-critical adjustment which permits the equivalent reactance of the secondary winding 5 to be readily varied by infinitely small amounts.

Referring now to Figs. 12, 13 and 14, the transformer T here shown comprises a stationary laminated magnetizable core 30 having three parallel legs 30*, 30 and 30 connected together at their lower ends by a. backstrap 30. .The leg 30 is provided with a primary winding P, and the leg 30 is provided with a secondary winding S. Formed on the upper end of the legs 30' and 30 are aligned vertical tongues (H and 3|, respeetively, and slidably mounted on shoulders 32 formed on the legs 30* and 30 on opposite sides of the tongues 3 I and 3| are movable core members 33 and 34; Each of these movable core members is provided adjacent its opposite ends with longitudinal slots 35 and 35 which slots slidably receive clamping bolts 36 and 31, respectively, mounted in the tongues 3 I and 3 I, whereby the blocks may be clamped in adjusted longitudinal positions relative to the fixed core member. A notch 38 is formed in the under side of each of the movable core members 33 and 34 near the central portions of these blocks in such through the secondary winding S and which in-v cludes the tongue 3l on the leg 30, the movable core members 33 and 34, the tongue 3|- on the leg 30, the leg 3|) and the backstrap30 and the remainder of the resultant flux will traverse a leakage path which includes the tongue 31 on the leg 30 the movable core members 33 and 34, the leg 30', and the left-hand half of the backstrap 30 the amount of the flux which traverses each path being dependent upon the relative reluctances of these two paths. The parts are so proportioned that when both movable core members 33 and 34 occupy their extreme righthand positions, the flux path through the secondary winding S will have a relatively low reluctance, and the leakage path will have a relatively high reluctance, but that, as either movable member is moved toward the left, the reluctance of the flux path through the leakage path will decrease and the reluctance of the flux path through the secondary winding will increase, un-

til when both members occupy their extreme lefthand positions, the reluctance of the path through the secondary winding will be relatively high, and the reluctance of the leakage path will be relatively low. It follows, therefore, that by adjusting the two movable core members 33 and 34 the relative reluctance of the flux path through the secondary winding and the leakage path may be readily adjusted in a manner to provide any desired variation in the equivalent reactance of the secondary winding between its maximum and minimum reactance.

One advantage of transformers embodying our invention is that since the reluctance of the magnetic path through the secondary winding is increased at the same time that the reluctance of the leakage path is decreased, the equivalent reactance of the transformer may be varied over a much wider range than has heretofore been possible.

Another advantage of transformers embodying our invention is that finer adjustments of the equivalent reactance of the transformers may be made than has heretofore been possible.

Although we have herein shown and described only a few forms of transformers embodying our invention, it is understood that various changes and modifications may be made therein within the scope of the appended claims without departing from the spirit and scope of our invention. Having thus described our invention, what we claim is: V

1. A reactive transformer comprising a stationary core member provided with three parallel legs connected at one end by a backstrap, a movable core member mounted for longitudinal sliding movement between two extreme positions at the ends of said legs opposite to said backstrap in such manner than one flux path is formed by a first one of said legs. a second one of saidlegs and said movable member and another flux path is formed by said first leg, the remaining leg, and said movable member, and that movement of said member from one extreme position toward the other will simultaneously increase the reluctance of one path and decrease the reluctance of the other path, said movable member being provided adjacent its ends on the side nearest said stationary core member with inclined surfaces which cooperate with the adjacent legs of said stationary core member in such manner that the reluctances of said two flux paths will vary uniformly in response to the movement of said movable member, a primary winding disposed on said first leg only, and a secondary winding disposed on said second leg only.

2. A reactive transformer comprising a stationary core member provided with three parallel legs connected together at their lower ends by a backstrap, a movable core member mountedjfor longitudinal movement between two extreme positions at the upper ends of said legs in such manner that when said movable core member occupies its one extreme position a low reluctance path will be formed from the one outer leg of said stationary core member to the other outer leg through said movable core member and a high reluctance path will be formed from said one outer leg to the middle leg of said stationary core member through said movable core member, but that movement of said movable core member toward its other extreme position will increase the reluctance of the flux path from said one outer leg to said other outer leg through said movable core member and will decrease the reluctance of the flux path from said one outer leg tojsaid middle leg through said movable core member, a primary winding on said one outer leg, and a secondary winding on said other outer leg.

3. A reactive transformer comprising a stationary core member provided with three parallel legs connected together at their lower ends by a backstrap, the two outer legs of said stationary core member being provided at their upper ends with aligned vertical tongues and with shoulders on one side of said tongues, a movable core member mounted for longitudinal sliding movement on said shoulders and provided in its under side with a notch which forms an air gap between said movable core member and said middle leg i when said movable core member occupies its one extreme position but not when it occupies its other extreme position, a primary winding on one of said outer legs and a secondary winding on the other outer leg.

4. A reactive transformer comprising a stationary core member provided with three parallel legs connected together at their lower ends by a backstrap, the two outer legs of said stationary core member being provided at their upper ends with aligned vertical tongues and with a shoulder on each side of said tongues, two movable core members one mounted for longitudinal sliding movement on the two shoulders on the one side of said tongues and the other mounted for longitudinal sliding movement on the two shoulders on the other side of said tongues, each of \said movable core members being provided in its under sidewith a notch which forms an air gap between such movable core member and said middle leg when such movable core member occupies its one extreme position but not when it occupies its other extreme position, a primary winding on one of said outer legs and a secondary winding on the other outer leg.

' 5. A reactive transformer comprising a stationary core member provided with three parallel legs connected together at their lower ends by a backstrap, the two outer legs of said stationary core member being provided at their upper ends with aligned vertical tongues and with shoulders on one side of said tongues, a movable core member mounted for longitudinal sliding movement on said shoulders and provided in its under side with a notch which forms an air gap between said movable core member and said middle leg when said movable core member occupies its one extreme position but not when it occupies its other extreme position, means for locking said movable core member in an adjusted longitudinal position, a primary winding on one of said outer gs and a secondary winding on the other outer leg.

6. A reactive transformer comprising a stationary core member provided with three parallel legs each connected together at one end by a backstrap, a bolt mounted in said middle leg at the end opposite to said backstrap, two movable core members disposed on opposite sides of said middle leg and each provided witha longitudinal slot which slidably receives said bolt, whereby said core members may be moved toward or away from each of said outer legs to adjusted positions and may be locked in their adjusted positions by said bolt, a primary winding on said middle leg, and a secondary winding on one of said outer legs.

'7. A reactive transformer comprising a stationary core member provided with three parallel legs each connected together at one end by a backstrap and each provided at the other end with a tongue and with a shoulder on each side of said tongue, a bolt mounted in the tongue in said middle leg, two movable core members slidably mounted on said shoulders on opposite sides of said tongues and each provided with a longitudinal slot which slidably receives said bolt, a primary winding on said middleleg and a secondary winding on one of said outer legs.

8. A reactive transformer comprising a stationary core member provided with three legs connected at one end by a back strap, a movable core member mounted for longitudinal sliding move ment between two extreme positions at the ends of said legs opposite to said back strap in such manner that a first variable reluctance flux path is formed by a first one of said legs, a second one of said legs and said movable core member, and a second variable reluctance flux path is formed by said first leg, the third one of said legs and said movable member, the parts being so proportioned that said one flux path will have a relatively high reluctance and said other flux path a relatively low reluctance or vice versa according as said movable core member occupies its one extreme position or its other extreme position and that movement of said movable core member will simultaneously vary the reluctances of said two paths in such manner that an increase in the reluctance of either path will be accompanied by a decrease in the reluctance of the other path, a primary comprising a single winding surrounding said first leg only, and a secondary comprising a single winding surrounding said second leg only.

9. A reactive transformer comprising a stationary core member provided with three parallel legs, two guide plates secured to the opposite sides of said stationary core member at one end of said legs, a movable core member mounted for longitudinal sliding movement between two extreme positions in the-channel formed by said guide plates in such manner that one flux path is formed by a first one of said legs, a second one of said legs and said movable core member and another flux path is formed by said first leg, the remaining leg and said movable core member, and that movement of said movable core member from one extreme position toward the other will simultaneously increase the reluctance of one path and decrease the reluctance of the other path, means for moving said movable core member between its two extreme positions, means associated with said plates for locking, said movable core member in any position to which it is moved, a primary winding surrounding said first leg, and a secondary winding surrounding said second leg.

10. A reactive transformer comprising a stationary core member provided with three parallel legs, two guide plates secured to the opposite sides of said stationary core member at one end of said legs, a movable core member mounted for longitudinal sliding movement between two extreme positions in the channel formed by said remaining leg and said movable core member,

and that movement of said movable core member from one extreme position toward the other will simultaneously increase the reluctance of one path and decrease the reluctance of the other path, means mounted in one of said guide plates and operatively connected with said movable core member for moving said movable core member between its two extreme positions, a bolt extending through and cooperating with said plates in such manner that when said bolt is tightened said movable core member will be firmly locked in any position to which it is moved, a primary winding mounted on said first leg, and a secondary winding mounted solely on said second leg.

11. A reactive transformer comprising a stationary core member provided with three parallel legs connected together at one end by a back strap, two guide plates secured to the opposite sides of said stationary core member at being provided at one end with a lateral exten sion and at each end with a longitudinally extending slot, and the other guide plate being provided at each end with a longitudinally extending slot which aligns with one of the slots in the opposite guide plate, a movable core member mounted in the channel formed by said guide plates for longitudinal sliding movement between two extreme positions in such manner that one flux path is formed by a first one of said legs. a second one of said legs and said movable core member and another flux path is formed by said other path, two bolts extending through said movable core member adjacent its ends and cooperating with the inner ends of the aligned slots in said guide plates to prevent movement oi said movable core member beyond its extreme positions, a screw threaded ,rod fastened at one end to said movable core member by one 01' said bolts and provided at its other end with a thumb nut rotatably mounted in said lateral extension 0! said one guide plate, whereby by turning said thumb nut in opposite directions said movable core member may be moved to any position between its two extreme positions, a primary winding mounted on said first leg or said stationary core member, and a secondary winding mounted on said second leg of said stationary core member.

SAMUEL M. LUCAS. CONRAD H. ZIERDT. 

